Interference elimination



.l \E I M 7, A 2 n INTERFERENCE ELIMINATION Filed July 28, 1925 Patented Oct. 27, 1931 UNITED STATES GEORG VON ARGO, OF BERLIN, GERMANY, ASSIGNOR TO GESELLSCHAIT FOR DRAHT LOSE TIEILEGRAPHIE M. B. E, OF BERLIN, GERMANY, A. CORPORATION OF GERMANY INTERFERENCE ELIMINATION Application filed July 28, 1925, Serial No.

My invention relates broadly to receiversfor receiving intelligence by means of high frequency electromagnetic waves and, more particularly, to a receiver which will eliminate disturbances due even to a local source.

An object of my invention is to provide a receiver having a rej ect-or circuit, as a by-pass circuit, for decreasing the efi'ect of dist-urbances upon the receiver.

Another object of my invention is to provide a receiver having for a -by-pass circuit a rejector circuit which has a relatively high admittance by virtue of having connected 111 it only a. relatively few turns constituting the secondary of a high ratio transformer. v p

A still further object of the invention is to provide a receiver having a blocking or rejector circuit arranged as a by-pass circuit for decreasing the disturbance across the receiving circuit with a damping reduction device which preferably makes use of the feed back from an electron discharge tube.

Other objects will be apparent from the following description and appended claims when considered with the accompanying drawing in which the single figure represents a receiver provided with an arrangement according to the invention.

In order to preclude marked disturbances due to neighboring transmitters from receiving systems, the suggestion is made to insert a blocking or trap circuit tuned to the frequency of the disturbance in the aerial. Another suggestion is to provide in parallel relation to the coupling means of the recelving apparatus, a circuit which is tuned to the incoming waves. In this latter case, this circuit offers a low resistance to all frequencies-with the exception of that of the transmitter to be received relative to which it acts as an infinite impedance.

Both arrangements, if used exactly as so far described, may be regarded as of equivalent effectiveness. Now, the present invention is restricted to the second arrangement, and I have been able to make it quitesubstantially superior to the, first one, so far as freedom from disturbance is concerned.

The means to that end consists in utilizing damping reduction in an aerial equipped with 46,535, and in Germany August 29, 1924.

a parallel-connected blocking circuit, it being immaterial in this connection whether the arrangement operates with high frequency amplification and a subsequent audion tube, or whether reduction of damping acts through back-coupling of the first tube alone, or that of the audion by wav of the first tube as far as the aerial, that is, through two tubes.

The reduction of damping does not only extend to cover the antenna, but it also includes the blocking circuit connected in parallel with the apparatus. This means that the backcoupling must be strengthened or the heating increased, when the tuned blocking circuit arranged in parallel is inserted, and if the same signal strength as in the absence of said circuit shall be obtained.

The blocking circuit becomes especially effective, if it does not consist merely of a simple oscillation circuit, i. e., of a condenser and inductance coil, but if said coil is furnished with a secondary winding comprising a few turns so that there results a high frequency transformer.

For instance, if the coil connected with the condenser comprises from 20 to 40 turns, from 1 to 4 turns are chosen for the secondary, the latter then constituting the shortcircuit properly so-called for the disturbing wave. The practical result is the same as if in parallel with relation to only a few turns a very large condenser involving no losses were arranged whose capacitance is so much larger than corresponds to the real ratio of transformation between the windings.

Referring now more particularly to the drawing, 1 denotes the antenna circuit having tuned reactances comprising an inductance coil 10 and capacitance 11 in series therewith. Connected across inductance 10 is the input or grid filament circuit of threeelectrode electron discharge tube 20.

This tube is well known in the art and comprises a heated filamentary cathode, a cold anode and a control electrode in the form of a grid, all sealed within an evacuated envelope.

In series with the grid is a condenser 12. while connected from grid to filament is grid leak 13.

tion ratio, and means including a feed-back Connected across both the inductance 10 and capacitance 11 is the secondary winding 3 of transformer 4 whose primary 5 is connected with condenser 2. As pointed out above, this transformer has preferably a variable ratio of transformation, the order of the ratio being such that, if 20 to 40 turns are used for the primary, 1 to 4 turns are used for the secondary. This makes the preferred ratio within the limits of l to 10 to l to 20. The condenser 2 is so adjusted that the transformer circuit across the inductance 10 and capacitance 11 is tuned to the signal frequency, acting as a block or trap thereto.

In the anode-filament circuit or output. circuit of tube 20 is connected in series a feed-back coil 21, source of anode current 22 and indicating device 23 which may be a telephone. Telephone 23 has preferably a condenser 24 in parallel therewith to bypass the high radio frequencies.

Feed-back coil 21 is coupled to transformer 4 to provide the necessary feed-back to the auxiliary circuit including transformer 4 and condenser 2. This feed-back, as pointed out above, reduces the damping, thereby greatly enhancing the value of the auxiliary circuit.

Having described my invention, I am entitled to all modifications as come fairly within the spirit and scope of my invention as defined in the following claims:

1. In combination, a receiving conductor adapted to receive desired signals and disturbances, a receiving circuit including an electron discharge tube coupled to said conductor. an auxiliary circuit for decreasing the effect of said disturbances on said receiving circuit, means for coupling said auxiliary circuit to said conductor including a transformer having a variable and relatively high transformation ratio, and means including a feed-back circuitfrom said tube for decreasing the damping in said auxiliary cirh cuit.

2. In combination, a receiving conductor adapted to receive desired signal energy and disturbances, a receiving circuit including an electron discharge tube coupled to said conductor, an auxiliary circuit for decreasing the effect of said disturbances on said receiving circuit, means for coupling said auxiliary circuit to said conductor including a transformer having a relatively high transforma circuit from said tube for decreasing the damping in said auxiliary circuit.

In combination. an antenna, a regenerative receiver having a feed back circuit, means to couple the antenna thereto, a stepdown transformer, a by-pass circuit for the coupling means containing the secondary of the step-down transformer, a. variable condenser connected across the primary of said transformer whereby the primary circuit may be made resonant for a desired freequency in order to introduce in the by-pass circuit high impedance for energy of the desired frequency, but relatively little impedance for energy of any other frequency and means coupling the feed-back circuit of the regenerativereceiver to the antennacircuit and the transformer in order to reduce the damping efiect of said feed-back circuit.

4. In combination, an antenna, a receiver, means to couple the antenna thereto, a stepdown transformer, a by-pass circuit for the coupling means containing the secondary of the step-down transformer, a variable condenser connected across the primary of said transformer whereby the primary circuit may be made resonant for a desired frequency in order to introduce in the by-pass circuit high impedance for energy of the desired frequency, but relatively little impedance for energy of any other frequency, and means to compensate for the resistance of said transformer circuit.

5. In combination, an antenna circuit including a tuned acceptor circuit, a by-pass circuit including a tuned rejector circuit connected in parallel with said acceptor circuit, both said circuits being tuned to the same desired wave, means to compensate for the resistance of both of said circuits, and a receiver coupled to said acceptor circuit.

6. In a radi col tuned carrier circuit having reactive means, a transformer having a high admittance secondary connected in parallel with said reactive means, apparatus including amplifying means coupled to said reactive means, tuning means connected to the primary of said transformer, and means to couple said amplifying means to said transformer primary circuit, said carrier circuit and said transformer circuit being tuned to the same frequency.

\ 7'. In combination an antenna circuit com'- prising an inductance coil anTa Eapacit'ance .in series, a space discharge device having input and output circuits, said input circuit being connected across said antenna induc- .tance, a condenser in saidinput circuit, aresistance connected across said c o r 1 de nser a step down transformer havingiits winding connected across said antepna condenser and inductance and its primary w inding in series with a variable condenser so as .to form a tunable circuit, said variable condenser being so adjusted that said tunable circuit is tuned to the signal frequency, a feed back coil, a source of current and a translatmg device all connected in series in said outimunication system, a

put circuit, said feed back coil being coupled to said transformer for reducing damping action in said tunable circuit.

GEORG VON ARGO. 

